In recent years, development of an optical-system untouched panel is being progressed, as an input unit of a personal computer and a portable terminal. The untouched panel makes it possible to input characters and draw a picture without touching a display with a fingertip. According to an optical-system touched panel, it is possible to suppress staining of a display surface, because a fingertip is not contacted to a display. Further, according to the optical-system untouched panel, a transparent electrode that detects touch of a fingertip to a display becomes unnecessary, because characters are input and a picture is drawn by detecting movement of a fingertip. Therefore, it is possible to suppress reduction of brightness of a display due to light absorption by the transparent electrode.
Further, in a game field, as a unit that transmits will of a person to a machine, there is distributed a system that changes movement of a man appearing on a screen or that changes movement of a man into a reaction to a ball, by causing the movement of the man to be optically recognized.
For a camera that is applied to the untouched panel and the system, a CMOS sensor or a CCD sensor is used as a solid-state image pickup device. For example, the CMOS sensor has plural pixels arrayed in a lattice shape, the pixel having equal sizes and also having the same sensitivity. In a case of detecting movement of a subject such as a fingertip by using a camera to which a CMOS sensor like this is applied, for example, it is necessary to perform the following signal process by using a movement-detection signal processing circuit.
That is, images of a predetermined region that includes a subject which moves in each predetermined time interval are picked up, and the picked up images are compared by using the movement-detection signal processing circuit. By comparing the images with each other, a direction to which the subject moved and a distance in which the subject moved are detected. Accordingly, the movement of the subject can be detected.
However, because this signal process is a process that is based on a comparison between the images, there is a problem in that the process is very complex and a processing time is also long.